Rotary cutting tool with tunable vibration absorber assembly for suppressing torsional vibration

ABSTRACT

A rotary cutting tool includes a tool body including a chip flute portion having a plurality of helical chip flutes separated by lobes. In one aspect, a tunable vibration absorber assembly is disposed within a cavity formed in the chip flute portion. In another aspect, the tunable vibration absorber assembly is disposed within a cavity of a replaceable cutting head. In each aspect, the tunable vibration absorber assembly includes at least two tunable absorber masses, a resilient material between the one or more absorber masses and the cavity, and one or more connecting members for preventing relative angular displacement of the one or more tunable absorber masses. The at least two tunable absorber masses are suspended only by the resilient material, thereby enabling the tunable vibration absorber assembly to be tuned to a desired frequency for suppressing torsional vibration of the rotary cutting tool during a cutting operation.

CLAIM TO PRIORITY

This application is a divisional application of application Ser. No.16/555,412, filed on Aug. 29, 2019, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

In general, the invention relates to a rotating cutting tool, and moreparticularly, to a rotary cutting tool, such as a twist drill, modulardrill, and the like, with a tunable vibration absorber assembly forsuppressing torsional vibration.

BACKGROUND OF THE INVENTION

During a metal cutting operation, any vibratory motion between a cuttingtool and workpiece may lead to undesirable cutting performances, such aspoor workpiece surface finish and out-of-tolerance finished workpieces.Furthermore, such vibration may cause the cutting tool or the machinetool to become damaged.

Torsional vibration in drills with helical flutes can generateoscillations in the axial direction due to the helical shape of theflutes, which in turn can cause chip thickness variation, therebyleading to chatter. Typically, the self-excited vibrations caused bytorsional (axial) vibration takes place at high frequencies andgenerates undesirable noise. This problem is particularly critical inlarge diameter modular drills and in rotating cutting tools with largelength/diameter (i.e., L/D) ratios.

Thus, there is a need to suppress or eliminate torsional vibrations in arotating cutting tool.

SUMMARY OF THE INVENTION

The problem of suppressing the torsional mode in a rotary cutting toolis solved by providing a tunable vibration absorber assembly having atleast two tunable absorber masses that follow the shape of the lobes ofthe flutes in the rotary cutting tool. The tunable absorber masses aresuspended by elastomer or other resilient support members. The materialproperties of the support members, such as stiffness, viscous damping,and the like, are selected in such a way that the torsional frequency ofthe tunable masses is set close to the torsional frequency of the drillbody. For better performance, the tunable masses are firmly connected toeach other. In one embodiment, the number of tunable masses is equal tothe number of flutes.

In one aspect, a rotary cutting tool comprises a tool body including achip flute portion having a plurality of helical chip flutes separatedby lobes; and a tunable vibration absorber assembly disposed within acavity formed in the chip flute portion. The tunable vibration absorberassembly comprises at least two tunable absorber masses, a resilientmaterial between the at least two tunable absorber masses and thecavity, and one or more connecting members for preventing relativeangular displacement between the at least two tunable absorber massesabout the central, longitudinal axis of the cutting tool. The one ormore connecting members do not contact the tool body to enable the atleast two tunable absorber masses to be suspended only by the resilientmaterial, thereby enabling the tunable vibration absorber assembly to betuned to a desired frequency for suppressing torsional vibration of therotary cutting tool during a cutting operation.

In another aspect of the invention, a rotary cutting tool comprises areplaceable cutting head; a tool body including a pocket portion forholding the replaceable cutting head and a chip flute portion having aplurality of helical chip flutes separated by lobes; and a tunablevibration absorber assembly disposed within a cavity formed in thereplaceable cutting head. The tunable vibration absorber assemblycomprises at least two tunable absorber masses, a resilient materialbetween the one or more absorber masses and the cavity, and one or moreconnecting members for preventing relative angular displacement betweenthe at least two tunable absorber masses about the central, longitudinalaxis of the cutting tool. The one or more connecting members do notcontact the replaceable cutting head to enable the at least two tunableabsorber masses to be suspended only by the resilient material, therebyenabling the tunable vibration absorber assembly to be tuned to adesired frequency for suppressing torsional vibration of the rotarycutting tool during a cutting operation.

In another aspect, a method of suppressing torsional vibrations in arotary cutting tool comprises disposing a tunable vibration absorberassembly within a cavity formed in the rotary cutting tool, the tunablevibration absorber assembly comprising at least two tunable absorbermasses, a resilient material between the one or more absorber masses andthe cavity, and one or more connecting members for preventing relativeangular displacement between the at least two tunable absorber massesabout the central, longitudinal axis of the cutting tool; and tuning thetunable vibration absorber assembly to a desired frequency by selectingone or more material properties of the at least two unable absorbermasses, the resilient material and the one or more connecting members,thereby suppressing torsional vibration of the rotary cutting toolduring a cutting operation.

BRIEF DESCRIPTION OF THE DRAWINGS

While various embodiments of the invention are illustrated, theparticular embodiments shown should not be construed to limit theclaims. It is anticipated that various changes and modifications may bemade without departing from the scope of this invention.

FIG. 1 is a perspective view of a rotary cutting tool, such as a modulardrill, with an internal tunable vibration absorber assembly according toan embodiment of the invention;

FIG. 2 is an enlarged cross-sectional view of the modular drill takenalong line 2-2 of FIG. 1 showing the tunable vibration absorber assemblyof the invention with tunable absorber masses having a fan-shapedcross-section disposed within the lobes of the modular drill;

FIG. 3 is a graphical representation of a simulated frequency responsefunction illustrating the tangential displacement (Y-direction) of atuned modular drill of the invention and a modular drill without thetunable vibration absorber assembly of the invention measured at aperiphery of the modular drill;

FIG. 4 is a graphical representation of a simulated frequency responsefunction illustrating the radial displacement (Y-direction) of a tunedmodular drill of the invention and a modular drill without the tunablevibration absorber assembly of the invention measured at a center of themodular drill.

FIG. 5 is a graphical representation of a simulated frequency responsefunction illustrating the axial displacement (Z-direction) of a tunedmodular drill of the invention and a modular drill without the tunablevibration absorber assembly of the invention measured at the center ofthe tip of the modular drill;

FIG. 6 is a graphical representation of a simulated frequency responsefunction illustrating the axial displacement (Z-direction) of a tunedmodular drill of the invention and a modular drill without the tunablevibration absorber assembly of the invention measured at a periphery ofthe modular drill.

FIG. 7 is an enlarged cross-sectional view of the modular drill takenalong line 2-2 of FIG. 1 showing the vibration absorber assembly of theinvention with tunable absorber masses having a circular-shapedcross-section disposed within the lobes of the modular drill;

FIG. 8 is a perspective view of a rotary cutting tool, such as a modulardrill, with an internal tunable vibration absorber assembly disposedwithin a replaceable cutting head according to an embodiment of theinvention;

FIG. 9 is an enlarged view of the replaceable cutting head of themodular drill of FIG. 8 with a tunable vibration absorber assemblydisposed within the replaceable cutting head according to an embodimentof the invention;

FIG. 10 is a side view of the replaceable cutting head of FIG. 8 withthe tunable vibration absorber assembly disposed within the replaceablecutting head according to an embodiment of the invention;

FIG. 11 is a cross-sectional view of the replaceable cutting head withthe tunable vibration absorber assembly disposed within the replaceablecutting head taken along line 11-11 of FIG. 10 ;

FIG. 12 is a top view of the replaceable cutting head of FIG. 8 with thetunable vibration absorber assembly disposed within the replaceablecutting head; and

FIG. 13 is a cross-sectional view of the replaceable cutting head ofFIG. 8 with the tunable vibration absorber assembly disposed within thereplaceable cutting head taken along line 13-13 of FIG. 12 .

DETAILED DESCRIPTION OF THE INVENTION

The description herein of specific applications should not be alimitation on the scope and extent of the use of the cutting tool.

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein. Identical parts areprovided with the same reference number in all drawings.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about”, “approximately”, and “substantially”, are notto be limited to the precise value specified. In at least someinstances, the approximating language may correspond to the precision ofan instrument for measuring the value. Here and throughout thespecification and claims, range limitations may be combined and/orinterchanged, such ranges are identified and include all the sub-rangescontained therein unless context or language indicates otherwise.

Throughout the text and the claims, use of the word “about” in relationto a range of values (e.g., “about 22 to 35 wt %”) is intended to modifyboth the high and low values recited, and reflects the penumbra ofvariation associated with measurement, significant figures, andinterchangeability, all as understood by a person having ordinary skillin the art to which this invention pertains.

For purposes of this specification (other than in the operatingexamples), unless otherwise indicated, all numbers expressing quantitiesand ranges of ingredients, process conditions, etc., are to beunderstood as modified in all instances by the term “about”.Accordingly, unless indicated to the contrary, the numerical parametersset forth in this specification and attached claims are approximationsthat can vary depending upon the desired results sought to be obtainedby the present invention. At the very least, and not as an attempt tolimit the application of the doctrine of equivalents to the scope of theclaims, each numerical parameter should at least be construed in lightof the number of reported significant digits and by applying ordinaryrounding techniques. Further, as used in this specification and theappended claims, the singular forms “a”, “an” and “the” are intended toinclude plural referents, unless expressly and unequivocally limited toone referent.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements including that found in the measuringinstrument. Also, it should be understood that any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.For example, a range of “1 to 10” is intended to include all sub-rangesbetween and including the recited minimum value of 1 and the recitedmaximum value of 10, i.e., a range having a minimum value equal to orgreater than 1 and a maximum value of equal to or less than 10. Becausethe disclosed numerical ranges are continuous, they include every valuebetween the minimum and maximum values. Unless expressly indicatedotherwise, the various numerical ranges specified in this applicationare approximations.

In the following specification and the claims, a number of terms arereferenced that have the following meanings.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where the event occurs and instances where it does not.

As used herein, the term “helical” is defined as pertaining to or havingthe form of a helix or spiral. A “helix” or “spiral” is defined as acurve in three-dimensional space formed by a straight line drawn on aplane when that plane is wrapped around a cylindrical surface of anykind, especially a right circular cylinder, as the curve of a screw. Acircular helix of radius a and slope b/a (or pitch 2πb) is described bythe following parametrization:x(θ)=a sin θ,y(θ)=a cos θ,z(θ)=bθ.

As used herein, the phrase “helix angle” is defined as the angle betweenany helix and an axial line on its right, circular cylinder or cone. Thehelix angle references the axis of the cylinder, distinguishing it fromthe lead angle, which references a line perpendicular to the axis. Thus,the helix angle is the geometric complement of the lead angle. The helixangle is measured in degrees.

As used herein, the helix of a flute can twist in two possibledirections, which is known as handedness. Most flutes are oriented sothat the cutting tool, when seen from a point of view on the axisthrough the center of the helix, moves away from the viewer when it isturned in a clockwise direction, and moves towards the viewer when it isturned counterclockwise. This is known as a right-handed (RH) flutegeometry, because it follows the right-hand grip rule. Flutes orientedin the opposite direction are known as left-handed (LH).

As used herein, the term “3D printing” is any of various processes inwhich material is joined or solidified under computer control to createa three-dimensional object, with material being added together, such asliquid molecules or powder grains being fused together, typically layerby layer. In the 1990s, 3D printing techniques were considered suitableonly to the production of functional or aesthetical prototypes and, backthen, a more comprehensive term for 3D printing was rapid prototyping.Today, the precision, repeatability and material range have increased tothe point that 3D printing is considered as an industrial productiontechnology, with the official term of “additive manufacturing”.

As used herein, the term “torsional vibration” is angular vibration ofan object, such as a shaft of a rotating cutting tool, along its axis ofrotation.

As used herein, the term “axial vibration” is vibration of an object,such as a shaft of a rotating cutting tool, along its axis of rotation.

Referring now to FIG. 1 , a rotary cutting tool 10 for conductingcutting operations on a workpiece (not shown) when the rotary cuttingtool 10 is rotated about a central, longitudinal axis 12 is shownaccording to an exemplary embodiment of the invention. Although depictedas a modular drill in the exemplary embodiment described herein, it isto be appreciated that the principles of the invention described hereinare applicable to other rotary cutting tools, such as, for example,without limitation, a solid carbide drill, a milling tool, a reamer, atap, an end mill, and the like.

The rotary cutting tool 10 is generally cylindrical and includes a firstor forward end 14 and an opposite, second or rearward end 16. The rotarycutting tool 10 has a tool body 11 that includes a pocket portion 17proximate the first end 14 for securely holding a replaceable cuttinginsert 50, and a chip flute portion 18 with at least two internaltunable absorber masses, as described in more detail below. The toolbody 11 can be made of tool steel, carbide, or any other suitablematerial. The replaceable cutting insert 50 can be made, for example, ofsolid carbide, or any other suitable material. The tool body 11 alsoincludes a mounting portion 20 proximate the second end 16 for mountingthe rotary cutting tool 10 in a chuck mechanism of a machine tool (notshown).

The chip flute portion 18 further includes a plurality of helical chipflutes 22 separated by lobes 23 extending rearwardly from the first end14 of the chip flute portion 18 to the mounting portion 20. Each chipflute 22 allows chips formed by the rotary cutting tool 10 to exit fromthe chip flute portion 18 during a cutting operation. Each chip flute 22has a helical geometry or pattern and are disposed at a helix angle 24relative to the central, longitudinal axis 12. In one embodiment, forexample, the helix angle 24 is at or about 30 degrees (+/−2 degrees).However, it will be appreciated that the invention is not limited by themagnitude of the helix angle 24, and that the invention can be practicedwith any desirable helix angle 24 in a range between about greater than0° and about 75°.

In the illustrated embodiment, the rotary cutting tool 10 includes twoflutes 22 (only one flute 22 is visible in FIG. 1 ) and two lobes 23.However, it should be appreciated that the invention is not limited bythe number of flutes 22 and lobes 23, and that the invention can bepracticed with a rotary cutting tool having any desirable number offlutes 22 and lobes 23, such as three, four, five, six, seven, eight,and the like.

FIG. 2 is a cross-sectional view of the chip flute portion 18 of thecutting tool 10 taken along a plane orthogonal to a plane lying alongthe central, longitudinal axis 12. Use of the rotary cutting tool 10 ina metalworking operation will produce vibrations that travel through thecutting tool 10, thereby affecting the stability of the cutting process.For this reason, the chip flute portion 18 of the rotary cutting tool 10includes a tunable vibration absorber assembly, shown generally at 60,for suppressing torsional and axial vibrations of the rotary cuttingtool 10, as shown in FIG. 2 .

In general, the tunable vibration absorber assembly 60 is disposedwithin a cavity 25 in each lobe 23 of the chip flute portion 18 and hasa length, L, along the central, longitudinal axis 12 of the cutting tool10. The tunable vibration absorber assembly 60 comprises at least twotunable absorber masses 62, a resilient material 64 disposed betweeneach tunable absorber mass 62 and the cavity 25, and one or moreconnecting members 66 for rigidly fixing each absorber mass 62 to eachother. The tunable vibration absorber assembly 60 has a forward end 63and a rearward end 65. In the illustrated embodiment, the modular drill10 has two flutes 22 and lobes 23. Thus, the tunable vibration absorberassembly 60 has two tunable absorber masses 62; one tunable absorbermass 62 following the twisted, helical path of one lobe 23 and anothertunable absorber mass 62 following the twisted, helical path of theother lobe 23.

It should be noted that the one or more connecting members 66 do notcontact the tool body 11, and thereby enabling the absorber masses 62 tobe supported or suspended only by the resilient member 64. As a result,the absorber assembly 60 can be tuned to the desired frequency, such asthe first natural frequency of a torsional vibration mode of the cuttingtool 10, by selecting one or more material properties of the tunablevibration absorber assembly 60. It should be noted that the tunablevibration absorber assembly 60 can be made using a 3D printing process(i.e., additive manufacturing).

The material for the absorber masses 62 is selected for its materialproperties, such as stiffness, density and the like. In one embodiment,the absorber masses 62 are made of the same material as the tool body11. For example, the absorber masses 62 can be made of tool steel,carbide, and the like. In another embodiment, the absorber masses 62 canbe made of a different material than the tool body 11. Typically, theabsorber masses 62 is made of a material that has a density equal to orgreater than the tool body 11. For example, the absorber masses 62 canbe made of lead, heavy metal, bronze, and the like, and the tool body 11can be made of tool steel, carbide, and the like.

Similar to the absorber masses 62, the resilient member 64 is selectedfor its material properties, such as stiffness, viscous damping,density, and the like. In one embodiment, the resilient member 64 ismade of a polymer with viscoelasticity (i.e., both viscosity andelasticity) with a generally low Young's modulus and high failurestrain, as compared to other materials. In one embodiment, the resilientmember 64 can be made of a commercially available fluoropolymerelastomer sold under the tradename VITON®, which is a registeredtrademark of The Chemours Company having headquarters in Wilmington,Del.

Similar to the tunable absorber masses 62 and the resilient member 64,the one or more connecting members 66 is selected for its materialproperties, such as stiffness, density, and the like. For example, thematerial for the one or more connecting members 66 has a sufficientstiffness to prevent relative angular displacement between the at leasttwo tunable absorber masses 62 about the central, longitudinal axis 12of the cutting tool 10. In the illustrated embodiment, the tunablevibration absorber assembly 60 includes two connecting members 66; oneconnecting member 66 proximate the forward end 63 and the otherconnecting member 66 proximate the rearward end 65 of the tunablevibration absorber assembly 60. The connecting members 66 can have anydesirable cross-sectional shape, such as circular, polygonal, and thelike, so long as the connecting member 66 prevents relative angulardisplacement between the absorber masses 62 about the central,longitudinal axis 12 of the cutting tool 10. The invention can bepracticed without the connecting members 66. However, it has been foundthat by preventing the relative angular movement between the absorbermasses 62 in relation to the central, longitudinal axis 12 of thecutting tool 10, the tunability of the vibration absorber assembly 60 isimproved because the connecting members 66 reduce the number of degreesof freedom of the tunable absorber masses 62. Also, it has been foundthat connecting the masses enables each absorber mass 62 to oscillate atthe same frequency and act as one large mass, instead of multipleindependent masses, thereby increasing the damping effect on the drill.

As shown in FIG. 2 , the cavity 25 is non-circular in cross-sectionalshape. Specifically, the cavity 25 has a geometry that maximizes thecross-sectional area of the absorber masses 62 without significantlyaffecting the overall stiffness of the cutting tool 10. In theillustrated embodiment, the cavity 25 has a fan-shaped cross-sectiondefined by a front planar wall 25 a extending in a radial direction ofthe cutting tool 10 on a front side of a rotation direction, RD of thecutting tool 10. The cavity 25 also includes a rear planar wall 25 bextending in the radial direction on a rear side of the rotationdirection, RD, of the cutting tool 10 and opposed to the front planarwall 25 a in a circumferential direction of the cutting tool 10. Anangle, A, is formed by the front planar wall 25 a and the rear planarwall 25 b. The angle, A, can be in a range between about 15° to about40°. The cavity 25 also has a radially outward arcuate wall 25 c made upof a partially cylindrical surface whose center lies on a center,longitudinal axis 12 of the cutting tool 10, and a radially inwardarcuate wall 25 d made up of a partially cylindrical surface whosecenter lies on the central, longitudinal axis 12 of the cutting tool.

FIG. 3 is a graphical representation of a simulated frequency responsefunction illustrating displacement in the tangential direction (i.e.,Y-direction) of a modular drill with the tunable vibration absorberassembly 60 of the invention and the same modular drill, but without thetunable vibration absorber assembly of the invention as measured at aperiphery of the modular drill. As shown in FIG. 3 , the displacement inthe tangential direction (i.e., Y-direction) at the periphery at thetorsional frequency of about 4100 Hz was reduced by a factor of aboutthirteen (13) in the modular drill with the tunable vibration absorberassembly 60 of the invention.

FIG. 4 is a graphical representation of a simulated frequency responsefunction illustrating displacement in the radial direction (i.e.,Y-direction) of a modular drill with the tunable vibration absorberassembly 60 of the invention and the same modular drill, but without thetunable vibration absorber assembly of the invention as measured at acenter (i.e., at the central, longitudinal axis 12) of the modulardrill. As shown in FIG. 4 , the radial displacement at a bendingfrequency of about 3200 Hz decreased by a factor greater than 4.5 at thecentral, longitudinal axis 12 of a modular drill with the tunablevibration absorber assembly 60 of the invention.

FIG. 5 is a graphical representation of a simulated frequency responsefunction illustrating displacement in the axial direction (i.e.,Z-direction) of a modular drill with the tunable vibration absorberassembly 60 of the invention and the same modular drill, but without thetunable vibration absorber assembly of the invention as measured at thecenter of the cutting tip of the modular drill. As shown in FIG. 5 , theaxial displacement (i.e., displacement in the Z-direction) at thetorsional frequency of about 4100 Hz was reduced by a factor of abouteight (8) in the modular drill with the tunable vibration absorberassembly 60 of the invention. It is known that the axial and angulardisplacement in drills is coupled due to the helical shape of theflutes. The reduction in amplitude of the angular displacement due todamping the torsional mode by way of the tunable vibration absorberassembly (FIG. 3 ) also causes a reduction in amplitude of the axialdisplacement.

FIG. 6 is a graphical representation of a simulated frequency responsefunction illustrating displacement in the axial direction (i.e.,Z-direction) of a modular drill with the tunable vibration absorberassembly 60 of the invention and the same modular drill, but without thetunable vibration absorber assembly of the invention as measured at aperiphery of the modular drill. As shown in FIG. 6 , the displacement inthe axial direction (i.e., Z-direction) at the torsional frequency ofabout 4100 Hz was reduced by a factor of about eight (8) in the modulardrill with the tunable vibration absorber assembly 60 of the invention.

In summary, the rotary cutting tool 10, such as a modular drill, thatincludes the tunable vibration absorber assembly 60 of the invention,produced the unexpected results of significantly reducing tangential,axial and radial displacement of the modular drill, as compared to thesame modular drill, but without the tunable vibration absorber assembly60 of the invention.

As mentioned above, the absorber masses 62 and the resilient member 64have a non-circular cross-sectional shape that conform to the shape ofthe cavity 25. However, it will be appreciated that the invention is notlimited to the cross-sectional shape of the absorber masses 62 and theresilient member 64, and that the invention can be practiced withabsorber masses and resilient members having any desirablecross-sectional shape.

Referring now to FIG. 7 , a tunable vibration absorber assembly 70 isshown according to another aspect of the invention. In this aspect thetunable vibration absorber assembly 70 has a substantially circularcross-sectional shape, rather than a fan-shaped cross-section of thetunable vibration absorber assembly 60. Thus, the cavity 25 has asubstantially circular cross-sectional shape. In addition, theconnecting members 76 also have a substantially circular cross-sectionalshape, unlike the connecting members 66 having a substantiallynon-circular cross-sectional shape. In the illustrated embodiment, thetunable vibration absorber assembly 70 has two connecting members 76;one connecting member 76 proximate a forward end 73 and the otherconnecting member 76 proximate a rearward end 75 of the tunablevibration absorber assembly 70. Similar to the connecting members 66,the connecting members 76 do not contact the tool body 11, therebyenabling the absorber masses 72 to be suspending or supported by theelastomer member 74.

As described above, the tunable vibration absorber assembly 60, 70 isdisposed within chip flute portion 18 of the modular drill 10.Specifically, the tunable absorber masses 62, 72 are disposed withineach lobe 23 of the modular drill 10. However, it should be appreciatedthat the invention is not limited by the location of the tunablevibration absorber assembly 60, 70 being located in the chip fluteportion 18 of the modular drill 10, and that the invention can bepracticed with the tunable vibration absorber assembly 60, 70 beingdisposed at any desirable location.

Referring now to FIGS. 8-13 , a modular cutting tool 100 is shownaccording to another embodiment of the invention. In the illustratedembodiment, the modular cutting tool 100 has a replaceable cutting head150 with a tunable vibration absorber assembly 80 disposed therein. Thetunable vibration absorber assembly 80 is generally similar in design asthe tunable vibration absorber 60 with absorber masses having afan-shaped cross-section, as shown in FIG. 2 . However, it should berealized that the tunable vibration absorber assembly 80 can be similarin design to the tunable vibration absorber assembly 70 with the tunableabsorber masses 82 having a substantially circular cross-section, asshown in FIG. 7 .

In general, the tunable vibration absorber assembly 80 is disposedwithin a cavity 125 in the replaceable cutting head 150 and has alength, L, along the central, longitudinal axis 12 of the modular drill100. Similar to the tunable vibration absorber assemblies 60, 70, thetunable vibration absorber assembly 80 comprises at least two tunableabsorber masses 82, a resilient material 84 disposed between eachtunable absorber mass 82 and the cavity 125, and one or more connectingmembers 86 for rigidly fixing each absorber mass 82 to each other. Inthe illustrated embodiment, the modular drill 100 has two flutes 22 andlobes 23. Thus, the tunable vibration absorber assembly 80 has twotunable absorber masses 82; one tunable absorber mass 82 following thetwisted, helical path of one lobe 23 and another tunable absorber mass82 following the twisted, helical path of the other lobe 23.

It should be noted that the one or more connecting members 86 do notcontact the cutting head body 11, and thereby enabling the absorbermasses 82 to be supported or suspended only by the resilient member 84.As a result, the absorber assembly 80 can be tuned to the desiredfrequency, such as the first natural frequency of the torsionalvibration mode of the cutting tool 100, by selecting one or morematerial properties of the tunable vibration absorber assembly 80. Itshould be noted that the tunable vibration absorber assembly 80 can bemade using a 3D printing process (i.e., additive manufacturing). It isbelieved that locating the absorber masses 82 closer to the cuttingedges of the replaceable cutting head 150 improves the effectiveness ofthe tunable vibration absorber assembly 80.

Although the rotary cutting tool 10 comprises a modular drill, it shouldbe appreciated that the principles of the invention can be practicedwith a solid drill, such as a solid carbide drill, in which the tunableabsorber masses are in the lobes of the solid carbide drill, similar tothe tunable vibration absorber assembly 60 shown in FIG. 2 .

The patents and publications referred to herein are hereby incorporatedby reference.

Having described presently preferred embodiments the invention may beotherwise embodied within the scope of the appended claims.

What is claimed is:
 1. A rotary cutting tool, comprising: a replaceablecutting head; a tool body including a pocket portion for holding thereplaceable cutting head; and a tunable vibration absorber assemblydisposed within a cavity formed in the replaceable cutting head, thetunable vibration absorber assembly comprising at least two tunableabsorber masses, a resilient material between the at least two tunableabsorber masses and the cavity, and one or more connecting members forpreventing relative angular displacement between the at least twotunable absorber masses about the central, longitudinal axis of thecutting tool, wherein the one or more connecting members do not contactthe replaceable cutting head to enable the at least two tunable absorbermasses to be suspended only by the resilient material, thereby enablingthe tunable vibration absorber assembly to be tuned to a desiredfrequency for suppressing torsional vibration of the rotary cutting toolduring a cutting operation.
 2. The rotary cutting tool of claim 1,wherein the at least two tunable absorber masses have a fan-shapedcross-section.
 3. The rotary cutting tool of claim 1, wherein the atleast two tunable absorber masses have a circular-shaped cross-section.4. The rotary cutting tool of claim 1, wherein the at least two tunableabsorber masses are made of a material having a density equal to orgreater than the tool body.
 5. The rotary cutting tool of claim 1,wherein the desired frequency corresponds to a first natural frequencyof a torsional vibration mode of the rotary cutting tool.
 6. The rotarycutting tool of claim 1, wherein the tunable vibration absorber assemblyis formed by additive manufacturing.